The present invention concerns a device for extruding sections from an ingot, in particular from a light metal extrusion ingot, by means of an extrusion die placed downstream from a container, whereby in front of the container i.e., upstream from it there is provided a tool for scalping the ingot, to remove its outer layer.
In hot forming an extrusion ingot, which has been heated to the extrusion temperature to shape it into elongated shapes or rods, the ingot which is normally surrounded by the container is pushed by the extrusion ram of a hydraulic press through the shaping tool or die. Whilst in the case of direct extrusion the container holding the ingot is moved towards the stationary die, in the so called indirect extrusion process the shape giving die is pushed into the fixed, stationary container. The die is situated at one end of a long stem which is both thermally and mechanically stressed; this stem is hollow since the extrusion formed passes out of the press through it.
Both with direct and indirect extrusion, difficulties arise due to segregation of elements in the ingot, impurities at the surface of the ingot and also to poor positioning of the ingot in the container. Furthermore, an oxide skin is formed due to oxidation of the ingot surface. In order to eliminate this a device was developed for the extrusion of metals and employs a cutting edge which is supported on a ring-shaped knife at the entry end to the container. During the charging of the ingot into the container, the stationary knife edge removes the surface layer of the ingot. The resultant ring of shavings is removed by means of blades specially employed for this purpose. It has however been found to be disadvantageous that a cutting edge of this kind involves considerable expense, and that its maintainance presents difficulties; also the scalping process can be carried out only at the expense of a considerable amount of time.
With this in mind the inventor set himself the task of improving a device of the kind described hereinabove and developing an economically attractive and time-saving scalping blade which scalps the surface of the ingot and also prevents the formation of an oxide skin between the scalping and extruding operations. Furthermore it should be possible to achieve an exact fit of the ingot diameter with respect to the inner diameter of the container.